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Excel Expertise: Oil Filters – 50 vs 25 microns.

A customer approached us with this question: Are 50 micron filters better than 25 micron filters when it comes to older Nordberg® cone crushers?

Excel crusher expert Ken Olson stepped in to field the inquiry, and this is what he had to say:

For years, Nordberg®, Symons®, HP®, MP®, and other various cone crushers used a 50 micron bag filter element with inside-to-out flow. This filtration method has been sufficient for the crushers, particularly the older Symons® models, but it is not truly the best option when it comes to filtering crusher lube oil. The use of 50 micron filters was in part due to the misguided fear that finer filtration would remove the particulate EP (extreme pressure) additives that were in use over 50 years ago. Current EP additives are in a solution in the oil and finer filtration will have no effect on these additives.

The other, and perhaps greatest, concern was the time and cost of frequently changing oil filters. The older cone crushers are significantly prone to rock dust contaminating the lubricating oil. This contamination necessitates frequently changing the oil filter elements. As most of these systems had filters over pressure relief valves, it was also common to have contaminated oil bypassed directly into the cone crusher once the filters became dirty.

In regards to the micron size of filter elements, there are a few aspects of key importance. The filtration industry actually classifies 50 micron oil filtration in the realm of pre-filtration and usually uses 40 micron as the break point to classify actual filtration. Some studies have been done with cone crushers that showed reduced bronze bushing consumption when the lubricating oil was filtered to remove finer particulate than was being removed by 50 micron filter elements. The contaminant’s diametric size does not have to be greater in diameter than the oil film thickness to create wear (abrasion). Wear can also occur with contaminants that are much smaller than the oil filter cut point (erosion).

Due to the advantages of going to finer filtration to remove particulate from lubricating oil, some cone crusher operators started using 25 micron filters. In order to experience longer filter element life, elements started to be made with a pleated fabric filter medium. Pleating the filtration fabric around an annular center opening greatly increases the actual filtration surface area over that of a bag filter, which is basically a cylindrical tube. In elements designed to work in place of the old Nordberg® 3894-081 (part number) bag filter, some pleated element filters have greater than 16 times more filtration surface area. The greater filtration surface allows for the capture of a much higher percentage of contaminants without decreasing the filter element life. Going away from a bag filter also allows for outside-to-inside oil flow, which makes it possible to build a much sturdier element without using a steel or heavy plastic structure to keep a bag from bursting under higher pressures.

Most crusher manufacturers have gone to the more modern pleated fabric element and use 25 micron filtration. Excel offers the conventional Nordberg® cone crusher filter elements in the pleated paper design at 50 (soon to be 40) and 25 micron, and the bag filter elements in 50 and 25 micron sizes.

-Ken Olson, Excel Service Manager

Ken Olson200 Excel Expertise: Oil Filters   50 vs 25 microns.

With over 30 years of experience in the mining industry and a degree in mining engineering, Ken Olson is a leader in the field. He helped develop the Raptor Cone Crusher line after joining Excel Crusher Technologies in 2004, and after joining Excel Foundry & Machine in 2012, he has been using his vast experience to greatly help the Excel team ever since.

Excel provides premium aftermarket components for more than a dozen different OEM brands. At Excel, we believe in delivering our distributors and customers quality products along with providing the very best in service and experience from industry experts.



All brand names, model names or marks are owned by their respective manufacturers. Excel Foundry & Machine, Inc. has no affiliation with the original equipment manufacturer. These terms are used for identification purposes only and are not intended to indicate affiliation with or approval by the OEM. All parts are manufactured by, for and warranted by Excel Foundry & Machine, Inc. and are not manufactured by, purchased from or warranted by the original equipment manufacturer.


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